There is a continuing need for packages for semiconductor dice that are compact, easy to manufacture and economical. There is a particular need for packages that can be used to make connections to terminals on both sides of the die. For example, vertical power MOSFETs, whether of the planar or trench-gated variety, typically have source and gate terminals on the front side of the die and a drain terminal on the backside of the die. The package must therefore provide connectibility to both sides of the die. Similarly, integrated circuits may need a ground contact to the front side to minimize transient effects.
Vertical trench MOSFETs, in particular, are now widely used in high-end electronic systems such as high-frequency DC-DC converters. These components are used in desktop and notebook computers and servers. In these applications it is critical that the MOSFETs have minimal electrical and thermal resistance.
U.S. Pat. No. 6,744,124 describes a semiconductor die package that has many advantages. The die, for example a trench MOSFET, is mounted in a flip-chip manner inside a cup-shaped lead frame. The drain terminal on the top side of the die is in electrical contact with the cup-shaped lead frame, which has leads that are configured to be coplanar with the bottom surface of the die, on which the source and gate terminals are located.
While the package described in the above-referenced patent has excellent electrical and thermal properties, there is still a need for a package that has even better thermal and electrical characteristics. Moreover, the package should be sufficiently rugged to be able to withstand numerous thermal cycles without failure and the lower surface of the die should be protected from scratching.